Dark Matter Search with CsI(Tl) crystal
scintillators : KIMS
HongJoo Kim (KyungPook National Univ.)
for KIMS collaboration
Windows on the Universe, Quy Nhon, Vietnam
Aug. 11-17, 2013
Yangyang Underground Laboratory
Korea Middleland Power Co.
(Upper Dam) Yangyang Pumped Storage Power Plant
Construction of Lab. buildings done in 2003
Gneiss (2 Gyr )
(Power Plant)
Depth
Minimum 700 m
Temperature
20 ~ 25 oC
Humidity
35 ~ 60 %
Rock contents
(Lower Dam)
238U
less than 0.5 ppm
5.6 ± 2.6 ppm
40K
270 ± 5 ppm
232Th
Muon flux
2.7 x 10-7 /cm2/s
Neutron flux
8 x 10-7 /cm2/s
Minimum
depth : 700 m / Access
to the lab by car (~2km)
222Rn in air
1~2 pCi/liter
WIMP search with CsI(Tl) Crystals
• Large mass with an affordable cost
 Good for AM study
• High light yield ~60,000/MeV
CsI(Tl) Crystal 8x8x30 cm3
• Pulse shape discrimination
3” PMT (9269QA) : Quartz
 Moderate background rejection ~5 Photo-electrons/keV
• Easy fabrication and handling
• Cs & I (SI cross section ~ A2)
Cs &,I are sensitive to SD interaction
Isotope
J
Abun
<Sp>
<Sn>
133Cs
7/2
100%
-0.370
0.003
127I
5/2
100%
0.309
0.075
73Ge
9/2
7.8%
0.03
0.38
129Xe
1/2
26%
0.028
0.359
131Xe
3/2
21%
-0.009
-0.227
nuclear recoil
(8.7 kg)
window, RbCs P.C.
electron recoil
KIMS (Korea Invisible Mass Search)
2000 @ CPL, began in the vinyl room
KIMS collaboration members
2003.2.27
Seoul National University: H.C.Bhang,
J.H.Choi, S.H. Choi, K.W.Kim, S.C.Kim,
S.K.Kim, J.H.Lee,J.I.Lee , J.K.Lee,
M.J.Lee, S.J.Lee, J.Li, X.Li,
S.S.Myung,S.L.Olsen, I.S.Seong
Sejong University: U.G.Kang, Y.D.Kim
Kyungpook National University:
H.J.Kim, J.H.So, J.Y.Lee
Yonsei University: Y.J.Kwon
Ewha Womans University: I.S.Hahn
Seoul City University : Douglas Leonard
Korea Research Institute of Standard
Sciences : Y.H.Kim, K.B.Lee, M.K. Lee
Tsinghua University : Y.Li, Q.Yue, J. Li
Mineral oil 30cm
12 x CsI(Tl) crystal
Copper shield
Boliden Lead 15cm : 30t
Polyethylene
Lead :shield
CsI crystal detector
OFHC Cu 10cm
3t
Moderator(Muon Det.)
KIMS with 104.4 kg CsI(Tl)
12 crystals(104.4kg) in operation
• 2.5 year data (Sep. 2009 – Feb. 2012)
• Background Level : 2~3 cpd/kg/keV
• Source calibration with 55Fe & 241Am
•Backgrounds are well understood.
Total backgrounds
Data
MC
Pulse shape discrimination
Nuclear recoil event rates (PSD analysis)
Pdf = f0 x FNR + f1 x FSA + (1-f0-f1) x Fgamma
The posterior pdf for f0 & f1 is obtained from
Bayesian analysis method.
1 year data excluding det0, 8, 11
Example : 6 keV bin, DET09
PSD result on WIMP search @KIMS
Total exposure: 24524.3 kg days
S.C. Kim et al., PRL 108 181301 (2012)
=> 3 years data analysis will be done.
SI WIMP-nucleon
SD WIMP-proton
Annual Modulation Derived From The Earth’s Orbit
3% of Total Rate
220km/s
Jun.
Dec.
30km/s
𝒗𝑬 (𝒕) ≈ 𝟐𝟐𝟎 + 𝟏𝟓 𝐜𝐨𝐬 (𝟐𝝅
𝒕 − 𝟏𝟓𝟐. 𝟓
) 𝒌𝒎/𝒔
𝟑𝟔𝟓. 𝟐𝟓
Annual Modulation Signals
DAMA/LIBRA
Eur. Phys. J. C 67 (2010) 39
CoGeNT
PRL 107 (2011) 141301
CDMS-II
arXiv:1203.1309v2
CDMS-II
CoGeNT
CDMS didn’t see
annual modulation
Data Taking
11

75.53 ton∙days
75.53 ton∙days during 2.5 years
Sep. 2009 ~ Feb. 2012
Sep. 2009 ~ Feb. 2012
Data taking :75.53 ton∙days during 2.5 years
Annual Modulation Fitting
2 Jun.
𝑓(𝑡) = 𝐴𝑑𝑒𝑐𝑎𝑦 𝑒 −
Decay
(𝑡−𝑡0 )
𝜏
+ 𝐵𝑘𝑔 + 𝐴 𝑐𝑜𝑠
Constant
Adecay : Initial level (134Cs)
t0 : Initial time – fixed to 1 Sep.
2009
τ : Decay constant (134Cs) –
fixed to T1/2=2.065 y
Bkg : Constant background
level
A : Annual Modulation
Amplitude
ω : Period – fixed to 1
year=365.25 d
t1 : Annual Modulation Peak –
fix to 2 June
2𝜋
(𝑡 − 𝑡1 )
𝜔
Modulation
Adecay
Bkg

2~6 keV : 0.0021±0.0062 (0.0122 90% CL Positive Limit), 3~6 keV : 0.0008±0.0068 (0.0119 90% CL
Positive Limit)
DAMA Result
2~4 keV : 0.0183±0.0082, 8.3σ

2~6 keV : 0.0021±0.0062 (0.0122 90% CL Positive Limit),

3~6 keV : 0.0008±0.0068 (0.0119 90% CL Positive Limit)
Spin-dependent
(WIMP-proton)
Spin-independent
(WIMP-nucleon)
Spin-dependent
(WIMP-neutron)
Spin-independent :
𝑆𝐼
𝜎𝑊−𝑛
=
2 1
𝜇𝑛
𝜎0 𝜇2 𝐴2
𝐴
,
Spin-dependent :
𝑆𝐷
𝜎𝑊−𝑛,𝑝
= 𝜎0
2
𝜇𝑛,𝑝
3
𝐽
1
2 4 (𝐽+1) <𝑆
2
𝜇𝐴
𝑛,𝑝 >
KIMS Perspectives
I. Upgrade of CsI(Tl) crystal detector
 Change PMTs to more sensitive and lower noise ones.
 Lower threshold ~ 1.5 keV, < 1 counts/(keV kg day).
II. KIMS-NaI



Duplicate DAMA experiment.
Develop ultra-low background NaI(Tl) crystals through international
collaboration (ANAIS, DM-ICE group @ south pole)
KIMS is ready to house NaI(Tl) crystals and 1st crystal will be installed
at Y2L this summer.
III. KIMS-CMO200 (AMoRE-DARK)
 natCanatMoO4 crystals with cryogenic technique : ~ 200 kg mass.
 High sensitivity in low mass WIMP.
 Good nuclear recoil separation is expected. Need to be developed.
WIMP search perspectives & KIMS
CoGent
CRESST
KIMS
upgrade
KIMS-PPC
CDMS
SuperCDMS
Buchmueller et al.
XENON
KIMS-CMO 200kg
XENON1T
Trotta et al.
Summary and Prospect




1 year data with 100 kg CsI(Tl) data analyzed with
PSD method. DAMA Iodine region is inconsistent with
KIMS nuclear recoil rate limit. 3 years data will
improve the sensitivity.
2.5 year data are analyzed without PSD for annual
modulation. The amplitudes of annual modulation are
0.0021±0.0062 cpd/kg/keV (2~6 keV) and
0.0008±0.0068 cpd/kg/keV (3~6 keV) which are
consistent with zero amplitudes within errors
Upgrade plans show further reduction of backgrounds
and NaI(Tl) R&D is underway. AMoRE-DARK will
explore not only 0-nbb search but also dark matter
search with cryogenic technique.
Center for Underground Nuclear, Particle, Astrophysics
(CUNPA) got funded : KIMS upgrade and AMoRE
project included.
Thank you for attention
Evidences for Dark Matter (~25% of Universe)
Rotation curve for Galaxy
Parameters of CDM by WMAP
Gravitational Lensing
Bullet cluster
19
Not visible, but gravitationally
evident!
Rencontres de Moriond 2012 (EW)
Energy Spectrum
20
2~4 cpd/kg/keV
Cut
Target
Electronics
Noise
electronics noise, …
Partial
Charge
PMT afterpulse, pileup signal, …
Spark Cut
PMT thermionic
electron, spark, …
Charge
Asymmetry
PMT scintillation or
Cherenkov, …
Signal
Start Time
PMT dark current, …
Time
Asymmetry
PMT dark current, …
Fit Quality
Cosmic signal’s tail,
…
EVENTS SELECTION
7 selection conditions are applied
MMC (Metallic Magnetic Calorimeter) for LTD
Principle of operation
1. Energy absorption in CMO crystal.
2. Phonon & Photon generation.
3. Temperature increase (gold film).
4. Magnetization of MMC decrease.
5. SQUID pickup the change.
Advantage of MMC
 Fast rising signal. (critical for lower
2nbb random coincidence.)
 Fairly easy to attach to absorber.
 Excellent Energy resolution
Large CMO crystal (216 g) was tested
paramagnetic sensor:
Au:Er
paramagnetic sensor: Au:Er
Energy Resolution
• 194 hour measurement at the overground laboratory (KRISS).
1461 keV
2615 keV
FWHM (keV) 8.85  0.62 9.94  1.28
Recent R&D result of Lucifer group.
arXiv:1303.4080v1
Dark matter sensitivity of CaMoO4 cryogenic experiment
CaMoO4
CDMS 2008
SuperCDMS 25kg
Eth=10 keV
(5 and 100 kg year)
XENON10 2007
Bottino et al
XENON100 6000 kgd
CMSSM, Ellis et al
CMSSM, Markov
chain Trotta et al
Eth=1 keV
(5 and 100 kg year)
Trotta et al
Ellis et al
Effective MSSM,
Bottino et al
by S. Scopel